Tray packaging machines are also referred to as “tray sealers” among experts. The most widely used type of such packaging machines is provided with one or a plurality of conveyor belts onto which the trays are placed and on which the trays are conveyed into a sealing station and out of the sealing station. To this end, the trays must, however, have a shape with a sufficiently large bottom area so that they will not shift, let alone fall over on the conveyor belts.
In another, also widely used type of packaging machines, the machines are provided with a tray conveyor including tray accommodation means. A conveyor of this type, configured as a plate chain, is disclosed in EP 1 038 773 B1. Such plate chains can ensure safe transport of the packaging objects accommodated therein, but they are cost-intensive and necessitate a great amount of maintenance work. In addition, plate chains can often only be used in combination with a special packaging machine and cannot be used on different types of packaging machines.
Another packaging machine is disclosed in EP 2 447 169 A2. The tray sealer described therein comprises, according to a first embodiment, a tray conveyor configured as a plate chain by means of which trays are supplied to and discharged from the tray sealer. The drawback of this arrangement is that the tray conveyor can only be used for a single type of trays and that changeover operations at the tray conveyor are time-consuming and cost-intensive. In addition, this tray conveyor can only be used in combination with special tray sealers, especially since the tool lower part and the tool upper part of the sealing station must be adapted to the plate chain conveyor. Finally, in practice excessively large distances between the individual trays exist in the case of a conveyor configured as a plate chain. This, however, also entails the restriction that an increased amount of cover-film waste material will have to be dealt with.
According to EP 2 447 169 A2 a frame member is used as a tray conveyor, which is shown in a schematic representation and by means of which a plurality of trays can be supplied to the tray sealer. After the sealing process, the empty frame members can be returned to the infeed station along a horizontal return facility, such as a rail. In the case of this embodiment, it is in particular problematic to accurately position the frame member during the sealing process relative to the tool lower part and the tool upper part of the tray sealer.
Another object carrier, which feeds a contact lens package to a sealing station, is disclosed in DE 603 18 868 T2.
DE 10 2008 030 510 A1 discloses a packaging machine with a gripper system. The gripper system collects from a feed belt a plurality of loose trays to be sealed and feeds them to a sealing station. Trays which have already been sealed are transferable from the sealing station to a discharge belt by means of the gripper system in the same operating cycle.
KR 101 104 401 B1 discloses another packaging machine including a tray conveyor configured as a plate chain where tray accommodation members are integrated in the plate chain and are intermittently fed to a sealing station.
Another conventional tray conveyor with integrated tray carriers is disclosed in Applicant's DE 199 12 491 A1. The plate chain disclosed therein is able to feed a plurality of trays to the sealing station per work cycle. This, however, leads to a high weight of the plate chain and necessitates a high input power.
DE 103 07 918 A1 discloses a method and a device for centering a cup in a cup filling machine. According to this method, the cup is centered in an opening provided in a cell plate by means of a suction device arranged below the cell plate.